The mouse int-2 gene exhibits basic fibroblast growth factor activity in a basic fibroblast growth factor-responsive cell line.
The int-2 protein is related to basic fibroblast growth factor (bFGF) by amino acid sequence homology. To assess its biological activity, we constructed retroviral vectors containing four variants of mouse int-2 complementary DNA under the transcriptional control of the beta-actin promoter and tested their effects on human SW13 adrenal cortical tumor cells. This cell line specifically requires bFGF, interleukin 1, or transforming growth factor e for anchorage-independent growth in soft agar. Despite encoding a signal sequence that should direct the protein to the secretory pathway, vectors containing unmodified int-2 complementary DNA, or a form optimized for translation initiation at the AUG codon, were incapable of inducing SW13 growth in soft agar. However, SW13 transfectants expressing a construct (pSP1), in which a mouse immunoglobulin signal peptide sequence is linked to the int-2 coding sequences, grew well in soft agar. The concentrated conditioned medium from these pSP1-transfected cells supported anchorage-independent growth of SW13 indicator cells and competed with bFGF for binding to receptors. Western blot analysis with an int-2-specific antiserum detected Mr 30,000-32,000 int-2 products in cell extracts and conditioned medium from pSP1-transfected clones, whereas the conditioned medium from these and other SW13 clones contained only low levels of bFGF as measured in a specific radioimmunoassay. These data suggest that the product of the int-2 gene can functionally replace bFGF in modulating the anchorage-independent growth of SW13 cells.
Merlo
G R
GR
Laboratory of Tumor Immunology and Biology, National Cancer Institute, Bethesda, Maryland 20892.
Blondel
B J
BJ
Deed
R
R
MacAllan
D
D
Peters
G
G
Dickson
C
C
Liscia
D S
DS
Ciardiello
F
F
Valverius
E M
EM
Salomon
D S
DS
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003470:Culture Media; D016222:Fibroblast Growth Factor 2 / Q000235:genetics*; D051518:Fibroblast Growth Factor 3; D005346:Fibroblast Growth Factors; D015870:Gene Expression / Q000502:physiology*; D005822:Genetic Vectors; D051379:Mice; D008969:Molecular Sequence Data; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology*; D011863:Radioimmunoassay; D011869:Radioligand Assay; D011994:Recombinant Proteins / Q000235:genetics; D012190:Retroviridae / Q000235:genetics; D014162:Transfection / Q000235:genetics
D003470:Culture Media; C489197:Fgf3 protein, mouse; D051518:Fibroblast Growth Factor 3; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D016222:Fibroblast Growth Factor 2; D005346:Fibroblast Growth Factors